Weiqing Wang

Fuzzy control used in variable speed wind turbine

Control of wind turbine generator system is very complicated because of the fluctuation and intermittence of wind speed and the complexity of power electronics. In classical control, the controller design needs accurate mathematical model, but this kind of model of the wind turbine generator system is very difficult to get because of the nonlinear characteristics. In order to obtain the maximum wind energy below rated wind speed, maintaining the optimum blade tip speed ratio is needed. In order to enhance the flexibility of gear system and get stable output power above rated wind speed, storing or delivering some energy in this condition is required. Using fuzzy controller, can simplify and avoid the sophisticated mathematical model. The fuzzy relations between the variables and the fuzzy rules were stated in detail. Simulation model and results are obtained. By using fuzzy controller, wind turbine generator system has better anti-interference property compared with the PID controller. The fluctuation of the power is minimized, the maximum power is traced and the rated power is maintained. The robust and stability of the designed fuzzy controller is also simply verified.

Summerization and study of fault diagnosis technology of the main components of wind turbine generator system

To find the fault of the wind turbine generator system early and to use proper measure to solve the fault in time and so to increase the operation efficient, the possible faults of the wind turbine generator system were analyzed. The possible faults occurrence of the different wind turbines used in Dabancheng wind farm were investigated. The fault diagnosis method of the wind turbine generator system was studied. The possible faults and the diagnosis method which can be used in the several main parts of the wind turbine generator system were summarized. The conclusion: The fault diagnosis method based on frequency spectrum analysis and wavelet analysis can be effectively used in the vibration analysis of the gear box, shaft and generator of wind turbine generator system. The frequency analysis, temperature field analysis and magnetic field analysis based on limited element analysis can be used in the fault mechanism analysis of the gear box and generator. The intelligent fault diagnosis method based on neural network and fuzzy theorem has significant application prospect in the fault diagnosis of the wind turbine generator system.

The intelligent control method study of variable speed wind turbine generator

Pitch control by controlling the pitch angle of the wind wheel blade of the wind turbine generator can control the rotation speed when the wind turbine generator is starting and the output power when the wind turbine generator is on grid. The wind wheel can get maximum wind energy when its blade tip speed ratio is an optimum value. When wind speed is less than the rated speed, the rotation speed of the wind turbine generator system should be controlled in order to get the optimum blade tip ratio. When wind speed is larger than the rated speed, the output power must be also controlled by changing the pitch angle of the blade according to the wind speed or the wind turbine will be damaged because of the over load. To get the maximum output power under lower wind speed and to maintain the stable rated output power under higher wind speed, the proper method must be used. In classical control, the controller design needs the accurate mathematical model of the wind turbine generator system, but this model is very difficult to get. To solve this problem, we use fuzzy controller to trace the maximum power when wind speed is lower than the rated speed and use neural network to get the proper pitch angle and so to limit the output power when the wind speed is greater than the rated speed. The simulation block diagram and simulation results were obtained. Compared with the PID controller, intelligent controller has better anti-interference property. The fluctuation of the power is minimized, the maximum power is traced and the rated power is maintained.

Individual pitch control based on fuzzy PI used in variable speed wind turbine

With increasing of the capacity and flexibility of the wind turbine generator system (WTGS), it is more and more important to make the operation even better and to reduce the load while the wind speed is above the rated speed of WTGS. The individual pitch control can solve the above two problem efficiently. But the control of WTGS is very complicated because of the fluctuation and intermittence of wind speed and the complexity of power electronics. In classical control, the controller design needs accurate mathematical model, but this kind of model of the wind turbine generator system is very difficult to get because of the nonlinear characteristics. Using fuzzy controller, we can simplify and avoid the sophisticated mathematical model. Combining with the studied method and results of other scholars about pitch control, we put forward the individual pitch control based on fuzzy PI control and used to control the wind turbine so that it can be more stable and meanwhile its operation load can be reduced, and the fluctuation of the power is minimized. Firstly, we use oscillation acceleration of one bladed as input and PI controller to get one pitch angle; secondly, we use rotation speed as input and use fuzzy PI controller to get a pitch angle; and thirdly, we use a distributed controller to get a pitch angle; finally, combine the three pitch angles and used as the real control pitch angles of the three blades. The simulation results are given in this paper.

The Intelligent Methods Used in Prediction the Wind Speed and Output Power of Wind Farm

The wind speed and wind power of wind farm prediction become more and more important as the increasing installation of wind turbines and the establishment of the large scale wind farms. Because the stochastic and intermittent property of wind speed, the prediction problem is very difficult to solve. The prediction method using BP neural network, wavelet BP neural network, and supported vector machine was studied in this paper. The simulation results shows that the method used in this paper can give a better prediction, but there is still more other algorithm need to be studied to enhance the prediction precision.

Matrix converter control study of doubly-fed induction wind turbine generator system

The one of the challenges faced by the large-scale development and use wind energy is the on grid requirement made by the power company. We use matrix converter to connect the rotor of the doubly-fed induction wind turbine generator system (DFIG) and the power grid. The indirect space vector modulation strategy and the constant switch frequency power control based on the matrix converter were proposed. The simulation model under the Matlab/Simulink software was built. The simulation curves were obtained. The simulation results proved that the matrix converter can be used in the DFIG and the proposed control method can realize the average power and the reactive power decoupled control. The simulation also verified that the control structure is simple, the control need not the PI control. The machine parameters have little influence to the control and the harmonics content is minor. The on grid power energy quality requirement about the wind power can be satisfied.

Voltage transient study of wind farm under power system fault

To study the voltage transient process of the wind farm when there is fault in the power system on which the wind farm connected, constant speed wind machine with squirrel cage induction generator and variable speed wind machine with double fed induction generator were discussed based on their operation principle and structure. Two kinds of wind farms built by only one of the two kinds wind machines were studied respectively. Simulation was done using the standard 9-bus-3-generator system. The main results are: First, the output voltage fluctuation of wind farm will different according to the different wind machine type. Second, the voltage transient process of wind farm while the power system in fault will also different according to the different wind machine type. Third, the voltage transient profiles are different according to the different places where the wind farm connected.

Noise forecast of large wind turbine based on regression analysis and GA-SVR

Wind turbine noise is important to environment and fault diagnosis and operation condition judgment. Aiming at complicated process of wind turbines noise detection, paper studied blade aerodynamic and the nacelle noise.To nacelle noise, put forward forecast noise sound pressure level by vibration parameters acceleration, simulate four kinds of typical operation conditions and consider influence of wind speed increase. Support vector machine regression based on genetic algorithm (GA-SVR) of the proposed ideas are verified. To blade aerodynamic noise, use non-acoustic parameters to predict noise A-weighted sound pressure level. The paper analyzed shortcomings of GA-SVR, and improvement was put forward. Termination conditions of GA was balanced. To predict noise by regression analysis combining with improved GA-SVR, prediction results is accurate and possess practical application value by the experiment verification.

Individual Pitch Controller for Power Quality Improvement on Megawatt Direct-Drive Wind Turbines

The aim of the designed pitch control algorithm is to improve the power quality and to reduce voltage flicker for megawatt direct-drive wind turbines. The simulation model of individual pitch controller and permanent magnet direct-drive wind turbine were developed by using the simulation tool of MATLAB. The short term flicker severity without fictitious Grid model is calculated based on IEC61400-21 because of no disturbance from other turbines. The individual pitch control method and the collective pitch action are compared. The active power and short-term flicker with full wind speed range under two controllers are simulated. The result indicates that the megawatt direct-drive wind turbines equipped with individual pitch controller exhibits good behavior with respect to output power and produce lower voltage flicker, especially for 3P frequency reduction.

The Study of on Grid Wind Turbine Generator Made in China

To study the on grid wind turbine generator made in china, three types of horizontal axis three-blade wind turbine generator were researched. The design of wind turbine and the factors which influence the property of the wind wheel were studied. The mathematical model and operation principle of wind turbine with squirrel cage induction generator, doubly-fed induction generator and permanent magnet synchronous generator were studied. The operation conditions of the wind turbine generators in Dabancheng wind farm were investigated. The conclusion is that all the three types of wind turbine generators can be used well according the wind condition of the wind farm. The variable speed wind turbine with doubly-fed induction generator and with permanent megnet synchronous generator have less influence to the power system and they can recover the power generation easier while grid fault is cleared compared with the wind turbine with squrrel-cage induction generator.